Bis phenols as stabilizers for organic materials



United States Patent STABILHZERS FDR ORGANIC MATERIALS James C. Boag, Detroit, Mich., assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Griginal application May 28, 1959, Ser. No. 816,399, new Patent No. 3,153,098 dated Oct. 13, 1964. Divided and this application June 4, .1964, Ser. No. 372,664

9 Claims. (Cl. 260-45.95)

The present invention deals in general with a novel class of compounds and their use as antioxidants. More particularly, this invention is concerned with a novel and unusual class of substituted phenolic compounds and the employment of these compounds as stabilizers and antioxidants for organic material.

It is the object of this invention to provide a novel class of chemical compounds. A further object of this invention is to provide novel compositions of matter comprising organic material stabilized against oxidative deterioration. A particular object of this invention is to provide high molecular weight unsaturated polymers of enhanced stability.

These and other objects are accomplished by a comnis PHENOLS AS pound having the formula:

HO OH Rz- I -Ri R2Cl-R1 A1 A1 (I) Where R is an organic hydrocarbon radical having from one to about 22 carbon atoms, R, is an alkyl radical having from one to three carbon atoms, R is selected from the group consisting of hydrogen and alkyl radicals having from one to three carbon atoms and A is an aromatic hydrocarbon radical having from six to about 12 carbon atoms. vention include: 4,4'- bis[2-tert-octyl-6-(a-ethyl-a-methylbenzyl) phenol] 4,4-bis[2-seceicosyl-6-(oa-methylbenzyl) phenol], 4,4 bis[2-(a,a-diisopropyl-p-n0nylbenzyl)-6- (a,a-diisopropyl-p-ethylpheny1benzyl)phenol], 4,4 bis- [Z-tert-amyl 6 (a,a-din1ethylbenzyl) phenol], 4,'4-bis- [2-methyl-6-(og-ethylbenzynphenol], 4,4 bis[2-ethyl-6- (u-diethyl-isobutylbenzyl phenol] 4,4-bis [2-tert-butyl- 6-(A-propyl 4 phenylbenzyDphenol], 4,4-bis[2-isopropyl 6-(a,a-dipropyl 3 hexylbenzyl)phenol], 4,4- bis[2-hexyl-6 (a-ethyl-a-methylbenzyl)phenol], 4,4-bis- [2, 6-dia,a-diethyl-4-methylbenzyl) phenol] A preferred embodiment of this invention is a compound having the formula:

where R and R are alkyl radicals having from one to three carbon atoms, R; and R are selected from the class consisting of hydrogen and the methyl group, and A and A represent aromatic hydrocarbon radicals having from six to about 12 carbon atoms. Among the compounds represented by this preferred embodiment are: 4,4-bis- [2,6 di (a,a-dimethylbenzyl)phenol], 4,4'-bis[2,6-di- (ct-ethyl 2 isopropylbenzyl)phenol], 4,4'-bis [2,6-di-(ocmethylbenzyl)phenol], 4,4 bis[2-(u-methylbenzyl)-6- (a,u-dimetl1ylbenzyl)phenol]. A particularly preferred embodiment of this invention consists of compounds of the above formula where R and R are methyl groups.

Examples of the compounds of this inice Thus, 4,4-bis[2,6-di-(a-methylbenzynphenol], 4,4-bis- [2,6-di-(a,c-dimethylbenzyl)phenol] and 4,4 bis[2-(amethylbenzyl) 6 (a,a-dimethy1benzyl)phenol] represent particularly preferred compounds of this invention. These compounds are preferred because of their unusual antioxidant activity and the fact that they are easily prepared from readily available starting materials.

Another preferred embodiment of this invention consists of those compounds in which R, in the formula first appearing above, is an alkyl group having from one to four carbon atoms, R is hydrogen or a methyl group and R is a methyl group. The particularly preferred alkyl groups represented by R are the methyl group, the isopropyl group and the tertiary butyl group. Examples 'ofthese preferred compounds are 4,4-bis[6-(a-methylbenzyl) o cresol], 4,4-bis[2-(a,a-dimethylbenzyl)-6- tert-butylphenol], 4,4 bis[6-(a,a-4-trimethylbenzyl)-ocresol], 4,4'-bis[2-(a-methyl-m-xylyl) 6 tert-butylphen01], 4,4 bis[6-(a,zit-3,4,5-pentamethylbenzyl)-o-cresol], 4,4-bis [2-isopropyl-6- a-methyl-2-ethylbenzyl) phenol]. I

a The novel compounds of this invention are particularly well suited as additives to organic material and particularly to high molecular weight elastomers as antioxidants. When thus employed the compounds have the desirable properties of low volatility and high stability. These properties are important in applications such as preserving rubber from oxidation. High volatility compounds tend to dissipate during rubber processing which is conducted at high temperatures. Thus, for an antioxidant to be effective, it must have low volatility and high temperature stability.

The compounds of this invention are readily prepared by oxidizing a phenol which is substituted in the 2 and 6 position with appropriate groups, to the diphenoquinone and subsequently reducing the diphenoquinone to the corresponding 4,4'-bis-(2,6-di-substituted phenol). For example, 4,4'-bis[6-(a-methylbenzyl)-o-cresol] is conveniently prepared by oxidizing 6-(oc-II1Gtl1Ylb6I1ZYl)-O-Cl'6SOl and subsequently reducing the thus prepared diphenoquinone to the desired compound.

The 2,6-di-substituted phenolic starting materials in this process have the formula:

1'32 R -(E-Ai (III) where R, R R and A are as defined above. These compounds are themselves prepared by reacting a phenol having the hydrogen atom on a carbon atom ortho to the hydroxyl group with an olefinic compound having an aromatic hydrocarbon radical bonded to one of the unsaturated carbon atoms, in the presence of an aluminum phenoxide catalyst. For example 6-(a-methylbenzyl-ocresol is convenientlyprepared by reacting ortho cresol with styrene in the presence of a small amount of aluminum o-cresoxide. This process is more fully described in application Serial No. 751,847, filed July 30, 1958, now Patent No. 3,075,832, and still further in a patent application filed March 26, 1959 by Alfred J. Kolka and George G. Ecke entitled Compositions of Matter, Serial No. 801,998, now abandoned.

A wide range of oxidizing agents may be employed in preparing the diphenoquinone precursers of the compounds of this invention. For example, such oxidizing agents as ferric chloride, nitric acid and chromic acid are conveniently employed.

agents as air, oxygen, hydrogen peroxide, various organic In addition such oxidizing .was stirred and heated at reflux for two hours.

ganate may be employed.

Reduction of the diphenoquinone is readily accomplished by the use of such reducing agents as zinc and acetic acid, stannous chloride and the like. The reduction of the diphenoquinone to the corresponding bisphenol may also be accomplished by catalytic processes employing hydrogen. Such catalysts as nickel-nickel oxide and pallacium chloride on charcoal are profitably employed as hydrogenation catalysts.

In the oxidation step, a wide range of temperature conditions may be employed. The reaction proceeds from about 40 C. and may be conducted up to about 150 C. However, temperatures in the range of 90 to 110 C. are preferred as high yields of diphenoquinone .are produced over this range with a minimum of undesirable side reactions and the reaction may be conducted in readily available simple equipment.

Similarly, a wide range of conditions may be used in the reduction of the diphenoquinone.

The following examples illustrate the compounds of this invention and their preparation:

EXAMPLE I In a reaction vessel fitted with heating means, reflux condenser and means for agitation was placed 60 parts of 2,6-di-(ot-methylbenzyl) phenol, 600 parts of methanol as a solvent, 200 parts of acetic acid and 70 parts of The mixture During the course of the reaction, a heavy red -oil slowly separated from the solution. This red oil, 3,3',3,5'-tetra-(amethylbenzyl)-4,4'-diphenoquinone was completely sepasodium dichromate in 100 parts of water.

rated from the reaction mixture by addition of 2,000

parts of water and subsequent separation. The oil was water washed and returned to the reaction vesselalong with 500 parts of methanol and 200 parts of concentrated hydrochloric acid. The resulting mixture was brought to reflux and powdered zinc was slowly added until a pale yellow solution resulted. After'dilution with water, a heavy oil separated which was recovered and stripped of unreacted 2,6-di-(a,a-methylbenzyl)phenol at up to 182 C. at 0.5 mm. of mercury. The resulting product was cooled and ground to a light yellow powder. Infrared analysis showed that this product was 4,4'-bis[2,6- dia-methylbenzyl) phenol].

EXAMPLE II In a reaction vessel equipped with heating means, means for agitation and means for passing gaseous reactants through a reaction mixture is charged 60 parts of 2,6-di-(a,u-dimethylbenzyl)phenol, 300 parts of ethanol and 20 parts of sodium hydroxide. This mixture while under agitation is treated with gaseous oxygen and the temperature is raised to 60 C. This oxygen treatment is continued for 6 /2 hours after which time the reaction mixture is cooled and made acid by the addition of 100 parts of acetic acid. The temperature is then raised to reflux and 15 parts of powdered zinc are slowly added. During the zinc addition, the color of the solution turns from dep red to light yellow. This reaction results in a good yield of 4,4'-bis[2,6-di-(ot,a-dimethylbenzyl) phenol] EXAMPLE III 4,4"- bis[2 tert butyl 6 (a ethyl a propylbenzy1)phenol is conveniently prepared by oxidizing 2- tert-butyl-6-(a-ethyl-u-propylbenzyl)phenol with ferric chloride using isopropanol as a solvent. During this oxidation the reaction mixture is kept acid through the use of acetic acid. This oxidation results in the diphenoquinone of the phenol employed. To reduce this diphenoquinone to the desired bis phenol a nickel-nickel oxide catalyst is employed. The catalyst is added to the reaction mixture which is raised to 40 C. and hydrogenpreparative examples.

is slowly bubbled through the mixture until the color of the diphenoquinone has completely disappeared.

EXAMPLE IV The procedure of Example III is followed using 6-(amethylphenzyl)-0-cresol as the starting phenol. The catalytic hydrogenation is conducted by employing palladium chloride on charcoal as catalyst. This reaction results in a high yield of 4,4'-[6-(a-me thylbenzyl)-ocresol].

. EXAMPLE V Example II is repeated using 2-ethyl-6-(a-ethyl-amethylbenzyl)phenol as the starting phenol. The oxidizing agent is supplied by rapidly bubbling air through the reaction mixture at the elevated temperature. Upon reduction with zinc in acid solution a good yield of 4,4- bis[2-ethyl-6-(a-methylbenzyl) phenol] is obtained.

EXAMPLE VI Example I is repeated employing 2-tert-octyl-6-a,a-diethyl-p-octylbenzyl)phenol. This reaction results in a good yield of 4,4'-bis[2-tert-octyl 6-(a,a-diethyl-p-octylbenzyl) phenol].

EXAMPLE VII 4,4 bis[2 isopropyl 6 (ot,ot diethylbenzyl)phenol] is prepared from 2-isopropyl-6-(a,a-dimethylbenzyl) phenol by the procedure employed in Example I.

Another part of this invention consists of bis phenol compounds prepared from a mixture of phenols, at least one of which is a phenol as defined by Formula III above. The mixture preferably contains at least about 20 mole percent of such a phenol, and the balance contains phenols which will oxidatively couple to a diphenoquinone. Thus, in addition to the phenol defined by Formula III above, the mixture contains at least 10 mole percent of a phenol having the formula:

R (IV) where R is as defined above and R is R or hydrogen, such that at least one R is R. When these mixtures of phenols are reacted to form diphenoquinones, a mixtures of several products results, and upon reduction to the bisphenol, a product is obtained which contains a supbstantial portion of an unsymmetrical bis phenol of the formula:

These asymmetric bis phenols may be separated from the reaction mixture, or may be used without separation. In both cases they are valuable antioxidants characterized by a higher degree of solubility in most organic media. This part of the invention is illustrated by the following EXAMPLE VIII The process of Example I is conducted using 26 parts i of 2,6-di-tert-butylphenol and 34 parts of 2,6-di-(a-rnethylbenzyl) phenol as starting materials. The product contains a substantial amount of 3,5-di-tert-butyl-3',5'-di-(ume thylbenzyl -4,4'-dihydroxydiphenyl.

EXAMPLE IX An equimolar mixture of 6-tert-butyl-o-cresol and 6-(a, a-dimethylbenzyl)-o-cresol is reacted as outlined in Example II. The product contains 4,4-bis(6-tert-butyl-ocresol), 4,4-bis[6-(a,a-dimethylbenzyl)-o-cresol] and 3, 3' dimethyl S-tert-butyl-S-(a,a-dimethylbenzyl)4,4-dihydroxydiphenyl.

EXAMPLE X i-Isopropylphenol and 2-(u-methylbenzyl)-6-(a,a-dimethyl)benzyl)-phenol in 1:9 molar ratio are reacted by the process of Example I to produce a mixture having excellent antioxidant activity.

Other asymmetric compounds according to this invention include: 2,4 dihydroxy-6-ethyl-3,5'-di-(ix-methylbenzyl)-diphenyl, 4,4 dihydroxy-2,3'-di-tert-butyl-5',-(aethylbenzyl)-diphenyl, 4,4-dihydroxy-3,3',S-tri-(a,adimethylbenzyl)5'-(a-propylbenzyl)-diphenyl and similar compounds.

The compounds of this invention are outstanding antioxidants. Therefore, an embodiment of this invention is a new composition of matter which comprises organic material normally tending to undergo oxidative deterioration in the presence of air, oxygen or ozone, containing a small antioxidant quantity, up to about five percent, of a compound of this invention as described in Formulas I and II above. A preferred embodiment of this invention consists of organic material containing those compounds in Which R in Formula I above is an alkyl group having one to four carbon atoms. In this class of compounds, the particularly preferred compoundsare those in which R is a methyl or tertiary butyl group. These compounds are particularly preferred since they tend to exhibit the most desirable properties and are readily prepared.

The compounds of this invention find important utility as antioxidants in a wide variety of oxygen sensitive materials. Thus, liquid hydrocarbon fuels such as gasoline, kerosene and fuel oil are found to possess increased storage stability by the use of an antioxidant of this invention. Likewise, liquid hydrocarbon fuels such as gasoline which contain organometallic additives such as tetraethyllead, as well as other organometallic compounds which are used as fuel additives, attain appreciably increased oxidative stability by the practice of this invention. In addition, lubricating oils and functional fluids, both those derived from naturally occurring hydrocarbons and those synthetically prepared, are greatly enhanced by the practice of this invention. The addition of small quantities of the compounds of this invention to such materials as turbine, hydraulic, transformer and other highly refined industrial oils, waxes, soaps and greases; plastics; synthetic polymers such as polyethylene and polypropylene; organometallic compositions such as tetraethyllead and tetraethyllead antiknock fluids; elastomers, including natural rubber; crankcase lubricating oils; lubricating greases;

and the like, greatly increase their resistance to deteriora tion in the presence of air, oxygen or ozone.

The compounds of this invention are also very useful in protecting petroleum wax-parafiin Wax and microcrystalline wax-against oxidative deterioration. They also find use in the stabilization of edible fats and oils of animal or vegetable origin which tend to become rancid especially during long periods of storage because of oxidative deterioration. Typical representatives of these edible fats and oils are linseed oil, cod liver oil, castor oil, soybean oil, rapeseed oil, coconut oil, olive oil, palm oil, corn oil, sesame oil, peanut oil, babassu oil, butter fat, lard, beef tallow, and the like.

The compounds of this invention are also very effective antioxidants for high molecular weight unsaturated hydrocarbon polymers, such as polybutadiene, methyl 6 rubber, polybutene rubber, natural rubber, butyl rubber, GRS rubber, GR- N rubber, piperylene rubber, dime-thyl butadiene rubber and the like. Thus, a preferred embodiment of the present invention is a rubber containing as an antioxidant therefor, 4,4-bis(2,=6-di-substituted phenol) as defined above. Another part of this invention is the method of preserving rubber which comprises incorporating therein a 4,4-bis(2,6-di-substituted phenol) of this invention as defined above. The stabilizer is incorporated into the rubber by milling, Banbury mixing, or similar process, or is emulsified and the emulsions added to the rubber latex before coagulation. In the various embodiments of this invention the stabilizer is used in small amounts, generally ranging from about 0.0 1 to about 5.0 percent, based on the rubber.

As used in the description and claims, the term rubber is employed in a generic sense to define a high molecular weight plastic material which possesses high extensibility under. load coupled with the property of forcibly retracting to approximately its original size and shape after the load is removed. It is preferable that the rubber be a sulfur-vulcanizab'le rubber, such as India rubber, reclaimed rubber, balata, gutta-percha, rubbery conjugated diene polymers and co-polymers exemplified by the butadiene-styrene (GR-S) and butadiene-acrylonitrile (GR-N or Paracril) rubbers and the like, although the invention isapplicable to the stabilization of any rubber, high molecular weight organic material which is normally susceptible to deterioration in the presence of oxygen, air, or ozone. The nature of these rubbers is well known to those skilled in the art.

Among the definite advantages provided by this invention is that the present rubber compositions posses unusually great resistance against oxidative deterioration. Furthermore, the novel stabilizer is relatively inexpensive and easily prepared, and possesses the highly beneficial property of low volatility. As is well known, a highly desirable feature of a rubber antioxidant is that it have .a low volatility so that it remains admixed with the rubber during vulcanization and related process steps.

Furthermore, the compounds of this invention impart excellent non-discoloration and non-staining characteristics to the rubber in which they are employed. In the manufacture of rubber items where a light colored rubber portion exists adjacent to a dark colored portion it is necessary that there be no migration of pigment from the dark to the light parts of the object. Thus, manufacturers of white sidewall tires must be sure that any antioxidant used in the white portion is non-staining and that any antioxidant used in the black portion will not migrate into the white portion and carry with it pigments which will discolor the white portion of the tire. In such application, the compounds of this invention have a marked advantage.

The rubber compositions of the present invention are illustrated by the following specific examples wherein all parts and percentages are by weight.

EXAMPLE XI Zinc oxide filler 50.00 Titanium dioxide 25.00 Stearic acid 2.00 Ultramarine blue 0.12 Sulfur 3.00 Mercaptobenzothiazole 1.00

butadiene-LB' and 32 percent of acrylonitrile.

v 4,4-bis [6-(a-methylbenzyl) -o-cresol]' is To the above base formula is added one part by weight of 4,4-bis[2,6-bis(a-methylbenzyl) phenol] and individual samples are cured for 20, 30, 45 and 60 minutes at 274 C. using perfectly clean molds with no mold lubricant. Another set of samples of the same base formula which do not contain an antioxidant are cured under the same conditions.

To demonstrate the protection afforded to the rubber ;by the practice of this invention, the tensile strength and the ultimate elongation of stocks prepared by the addition of the inhibitor are determined before and after aging. These properties are also determined on the inhibitor-free stocks. The aging is accomplished by conducting the procedure of ASTM designation: D-572-52, described in the ASTM Standards for 1952, Part 6, for a period of 168 hours at a temperature of 70 C. with an initial oxygen pressure in the test bomb of 300 p.s.i.g.

The tensile strength and the ultimate elongation of the test specimens before and after aging are measured by 'of the test specimens which occur during the accelerated aging. This is a direct measure of the oxygen up-take of the samples and provides another criterion of the effectiveness of an inhibitor in suppressing oxidative deterioration of the rubber. Thus, the larger the weight increase, the greater is the deterioration and the less is the inhibitor.

In all of the above tests, the composition compounded with 4,4 bis[2,6 -bis(a methylbenzyl)phenol] gives results which show this additive to be an excellent antioxidant.

EXAMPLE XII To a synthetic rubber master batch comprising 100 parts of GR-S rubber having an average molecular weight of 60,000, 50 parts of mixed zinc propionatestearate, 50 parts of carbon black, five parts of road tar, two parts of sulfur and 1.5 parts of mercaptobenzothiazole is incorporated 1.5 parts of 4,4'-biS[6-(oc,a-dimethylbenzyl)-o-cresol]. This batch is then cured for 60 minutes at 45 psi. of steam pressure.

EXAMPLE XIII Natural rubber stock is compounded according to the following formula:

This stock is then vulcanized for 60 minutes at 280 F.

' EXAMPLE XIV A butadiene-acrylonitrile copolymer is produced from Two percent (based onthe dry weight of the copolymer) of added as an emulsion in sodium -oleate solution to the latex obtained f from emulsion copolymerization of the monomers. The

latex is coagulated with a pure grade of aluminum sulfate and the coagulum, after washing, is dried for 20 hours at 70 C. p

EXAMPLE XV Three percent of 4,4-bis[2,6-bis(a-methylbenzyl) phenol] emulsified in sodium oleate is added to a rubberlike copolymer of butadiene-1,3 and styrene containing 25 percent of combined styrene. Y

EXAMPLE XVI A rubber stock is compounded fro'm 100 parts of smoked sheet rubber, 60 parts of zinc oxide, 20 parts of lithopone, 2 parts of sulfur, 0.7 part of diphenyl guanidine phthalate, 0.8 part of benzoyl thiobenzothiazole, 0.2 part of paraffin and 2 parts of 4,4-bis[2-(a,a-dimethylbenzyl)-6-tert-butylphenol]. The stock so compounded is cured by heating for 45 minutes at 126 C. in a press.

EXAMPLE XVII Two parts of 4,4"-bis[2-( t-ethyl-4-methylbenzyl)-6- ethylphenol] are incorporated in 100 parts of raw butyl rubber prepared by the copolymerization of percent of isobutylene and 10 percent of isoprene.

EXAMPLE XVIII To 200 parts of raw butyl rubber prepared by copolymerization of percent of isohutylene and 5 percent of butadiene is added 1.5 parts of the product of Example X.

EXAMPLE XIX To a master batch of GR-N synthetic rubber comprising parts of GR-N rubber, 5 percent of zinc stearate, 50 parts of carbon black, 5 parts of road tar, 2 parts of sulfur and 2 parts of mercaptobenzothiazole is added 5 percent based on the weight of the batch of 4,4'-bis[6- (a,a-dimethylbenzyl)-o-cresol] EXAMPLE XX To natural rubber (Hevea) is added 0.1 percent of the product of Example VIII.

Each of the above illustrated rubber compositions of this invention possesses greatly improved resistance against oxidative deterioration as compared with the corresponding rubber compositions which are devoid of an antioxidatnt. Moreover, the light-colored stocks of the above examples exhibit virtually no discoloration or staining characteristics even when subjected to severe weathering conditions and the like. The methods of formulating the improved rubber compositions of this invention will now be clearly apparent to those skilled in the art.

The amount of stabilizer employed in the rubber compositions of this invention varies from about 0.01 to about 5 percent by weight based on the weight of the rubber. The amount used depends somewhat upon the nature of the rubber being protected and the conditions of service to be encountered. 1 Thus, in the stabilization of natural and synthetic rubber to be used in the manufacture of tires which are normally subjected to exposure to the elements, as well as to the action of sunlight, frictional heat, stress and the like, the use of relatively high concentrations of this inhibitor is advantageous. On the other hand, when the article of manufacture is not to be subjected to such severe conditions, relatively low concentrations can be success-fully utilized. Generally speaking amounts ranging from about 0.1 to about 3 percent by weight give uniformly satisfactory results.

Other rubbers and elastomers which can be preserved according to this invention are the rubbery polymerizates of isoprene, butadiene-l,3, piperylene; also the rubbery copolymer of conjugated dienes with one or more polymerizable monoolefinic compounds which have the capability of forming rubbery copolymers with'butadiene- 1,3, outstanding examples of such monoolefinic compounds being those having the group CH exemplified by styrene. Examples of such monoolefins are styrene, vinyl naphthalene, alpha methyl styrene, p-chlorostyrene, dichlorostyrene, acrylic acid, methyl acrylate, methyl methacrylate, methacrylonitrile, methacrylamine, methyl vinyl ether, methyl vinyl ketone, vinylidihe chloride, vinyl carbazole, vinyl pyridines, alkyl-substituted vinyl pyridines, etc. In fact, excellent stabilization is achieved by incorporating a compound of this invention in any of the well known elastomers which are normally susceptible to deterioration in the presence of air, such as elastoprenes, elastolenes, elastothiomers, and elastoplastics.

As pointed out above, the compounds of this invention are effective antioxidants when added to other organic compositions normally tending to undergo deterioration in the presence of air, oxygen or ozone. The following examples illustrate various embodiments of this aspect of the invention.

EXAMPLE XXI To a master batch of high molecular weight polyethylene having an average molecular weight of about 1,000,000, a tensile strength of 6,700 psi, a Shore D hardness of 74 and a softening temperature under low load of 150 C. is added 5 percent of 4,4'-biS[2,6-bis(a,ocdimethylbenzyl) phenol] to prepare a composition of outstanding'oxidative stability.

EXAMPLE XXII A linear polyethylene having a high degree of crystallinity, up to 93 percent, and below 1 ethyl branched chain per hundred carbon atoms, a density of about 0.96 gram per milliliter and which has about 1.5 double bonds per hundred carbon atoms, is treated with 50x10- roentgens of fi-radiation. To the thus irradiated polymer is added 0.005 percent of 4,4'-bis[G-(a-methyIbenZyD- o-cresol] and the resulting product has better stability characteristics.

EXAMPLE XXIII Two parts of the product of Example IX are added with milling to 100 parts of a low density polyethylene prepared by high pressure polymerization and which has an average molecular weight of 18,000 to 20,000. The resulting product is vastly improved in its oxidative stability.

EXAMPLE XXIV To 10,000 parts of a polyethylene having an average molecular weight of about 100,000 and which has a tensile strength of 5400 p.s.i., a Shore D-hardness of 70 and a softening temperature of 130 C. under low load, is added 10 parts of 4,4'-bis[2,6-bis(a-methylbenzyl) phenol] to prepare a composition of outstanding oxidative stability.

Liquid hydrocarbon fuels employed in the operation of spark ignition combustion engines are also vastly improved in their storage stability by the practice of this invention. Table I, below, gives the compositions of a number of typical commercial gasolines which may be stabilized against oxidative deterioration by the inclusion therein of compounds of this invention.

.tions.

1 0 EXAMPLE XXV EXAMPLE XXVI To 10,000 parts of Gasoline B is added 500 parts of 4,4-bis[G-(a-methylbenZyl)-o-cresol] EXAMPLE XXVII To 10,000 parts of Gasoline C is added one the product of Example VIII.

Most gasolines in commercial use also contain an organometallic antiknock agent and certain scavengers therefor. The antiknock agent most frequently employed is tetraethyllead. The scavengers are ordinarily halohydrocarbon compounds of chlorine and bromine. Most widely used of these are ethylene dibromide and ethylene dichloride. In addition, gasolines often contain other additives such as dyes and phosphorus containing corrective agents. These gasoline compositions containing additives are also protected against oxidative deterioration by the practice of this invention as demonstrated by the following examples.

EXAMPLE XXVIII To 10,000 parts of Gasoline D, which contains 2.39 g./gal. of tetraethyllead and one theory of bromine as ethylene dibromide, is added parts of 4,4'-bis[2,6-di- (a,a-diisopropylbenzyl) phenol] EXAMPLE XXIX To 1,000 parts of Gasoline E, which contains 2.47 g./ gal. of lead as tetraethyllead, one theory of chlorine as ethylene dichloride, 0.5 theory of bromine as ethylene dibromide and 0.2 theory of phosphorus as tris(/i-chloroisopropyl)thionophosphate, is added 5 parts of 4,4-bis [6- a-ethyl-a-propyl-p-nonylbenzyl) -o-cresol] The tetraethyllead antiknock additive is supplied to oil companies as a mixture already containing the necessary dyes and scavengers. These mixtures, which are commonly known as antiknock fluid compositions, are also protected against oxidative deterioration by the practice of this invention.

EXAMPLE XXX To an antiknock fluid composition which is to be used as an additive to gasoline and which contains 61.5 parts of tetraethyllead, 17.9 parts of ethylene dibromide and 18.8 parts of ethylene dichloride is added with agitation 1.3 parts of 4,4'-bis[2,6-bis(a-methylbenzyl)phenol]; The resulting composition is stable for long periods when exposed to air.

EXAMPLE XXXI To 1,000 parts of commercially available diesel fuel having an octane number of 51.7 and a 50 percent evaporation temperature of 509 F. is added 3 par-ts of 4,4- bis[6-(u-methylbenzyl)-o-cresol]. The resulting fuel is stable to oxidative deterioration.

The compounds of this invention are also-useful in preventing oxidative deterioration in lubricating oil composi- Thus, an embodiment of this invention is a lubricating oils normally susceptible to oxidative deterioration containing a small antioxidant quantity, up to 5 percent, of a compound of this invention as defined above.

To prepare the lubricants of this invention, an appropriate quantityfrom about 0.001 to about 5 percent and preferably from about 0.25 to about 2 percentof the compound of this invention is blended with the base oil to be protected. Suitable base oils include mineral oils and also synthetic diester oils, such as sebacates, adipates, etc. which find particular use as aircraft instrument oils, hydraulic and damping fluids and precision bearing lubricants. All of these base oils are normally susceptible to part of- 1 l oxidative deterioration, especially at elevated temperatures.

The finished lubricants of this invention have much greater oxidation stability and many other improved performance characteristics as compared with the corresponding base oils.

The following examples illustrate the preferred lubricating oil compositions of this invention.

EXAMPLE XXXII To 1,000 parts of a solvent refined neutral oil (95 VI and 200 SUS at 100 F.) containing 6 percent of a commercial methacrylate type VI approver which gives the finished formulation of a VI of 140 and a viscosity of 300 SUS at 100 F. is added 5 percent of 4,4-bis[6-(a,adimethylbenzyl -o'-cresol] EXAMPLE XXXIII To an additive-free solvent refined crankcase lubricating oil having a viscosity index of 95 and a SAE viscosity of 10 is added 0.001 percent of 4,4'-biS[2,6di-(a,ocdimethylbenzyl phenol].

EXAMPLE XXXIV To 100,000 parts of a petroleum hydrocarbon oil having a gravity of 303 API at 60 F., a viscosity of 178.8 SUS at 100 F., a viscosity index of 154.2 and which contains 0.2 percent sulfur, is added 200 parts of 4,4-bis[2-(a,adiethyl-p-methylbenzyl)-6-tert-butylphenol]. The resulting oil possesses greatly enhanced resistance to oxidative deterioration.

EXAMPLE XXXV To 100,000 parts of a commercially available pe'ntaerythritol ester having a viscosity at 100 F. of 22.4 centistokes, and known in the trade as Hercoflex 600 is added 400 parts (0.4 percent) of 4,4-bis[2,6-di-( xmethylbenzyl)phenol1. The resulting finished oil possesses markedly improved resistance against oxidative deterioration.

EXAMPLE XXXVI To 100,000 parts of dioctyl sebacate having a viscosity of 210 F. of 36.7 SUS, a viscosity index of 159 and a molecular weight of 426.7 is added 250 parts (0.25 percent) of 4,4'-bis[6-(a-methylbenzyl)-o-cresol].

To illustrate the benefits obtained by the practice of this invention, a standard oil oxidation test is used. The equipment and test procedure described by Kroger et al., Erdol and Kohle, 2, page 398 (1949), served as a basis for the tests. The equipment and procedures are slightly modified in order to make the oxidizing conditions more strenuous. In this manner the test lubricants are subjected to severe oxidizing conditions in order to conclusively establish the elfectiveness of additives under very adverse conditions. Furthermore, the modifications are found to provide results which correlated extremely well with test results of other standard procedures, including actual engine tests.

The equipment consists of a reaction cell connected with an open end manometer whereby the total uptake of oxygen by the oil is determined by noting the drop in height of the mercury in the manometer. The test oil sample is placed in the reaction cell which is then flushed with oxygen and the temperature is then raised and held at that selected for the test until the substrate oil undergoes catastrophic oxidation which is known by a rapid oxygen uptake. In all cases, the test oil is deliberately contaminated with iron hexoate as an oxidation promotor. In t st at t i n tu e, the oxidation stab y o a e t where R is selected from the group consisting of alkyl radicals containing from 1 to 22 carbon atoms and benzyl radicals containing from 7 to22 carbon atoms, R is an alkyl radical having from 1 to 3 carbon atoms, R is selected from the group consisting of hydrogen and alkyl radicals having from 1 to 3 carbon atoms and A is an aromatic hydrocarbon radical having from 6 to 12 carbon atoms and which is selected from the group consisting of phenyl, diphenyl and alkyl substituted phenyl radicals.

2. Organic material normally tending to undergo oxidative deterioration containing a small antioxidant quantity, up to 5 percent, of a compound having the formula:

wherein R and R are alkyl radicals having from 1 to 3 carbon atoms; R; and R are groups selected from the class consisting of hydrogen and the methyl group, and A and A are aromatic hydrocarbon radicals having from 6 to 12 carbon atoms and which are selected from the group consisting of phenyl, diphenyl and alkyl substituted phenyl radicals.

3. The composition of claim 2 wherein said organic material is a high molecular weight diolefin polymer selected from the class consisting of natural rubber and synthetic diene rubber.

4. The composition of claim 2 wherein said compound is 4,4-bis [2,6-di-( oi-methyl-benzyl) phenol] 5. The composition of claim 3 wherein said compound is 4,4'-bis [2,6di- (a-methylbenzyl phenol]. I

6. The composition of claim 2 wherein said organic material is polyethylene.

7. The composition of claim 6 wherein said compound is 4,4-bis [2,6-di-(a-methylbenZyDphenol].

8. The composition of claim 2 wherein said organic material is polypropylene.

9. The composition of claim 8 wherein said compound is 4,4'-bis[2,6-di-(a-methylbenZyDphenol].

No references cited.

LEON J, BERCOVITZ, Primary Examiner, 

1. ORGANIC MATERIAL NORMALLY TENDING TO UNDERGO OXIDATIVE DETERIORATION CONTAINING A SMALL ANTIOXIDANT QUANTITY, UP TO 5 PERCENT, OF A COMPOUND HAVING THE FORMULA: 